In her masterpiece The Second Sex, Simone de Beauvoir depicts the atrocities of a typical patriarchal society. The author assumes that every human being should have the opportunity to experience feelings of a conquest and of being conquered to fully appreciate freedom. The body, the essential condition of human existence, is equally an object and a subject. Unfortunately, as Beauvoir reveals, this ontological rule is not respected in a society dominated by men. Patriarchy juxtaposes a male body, the subject, with a female body, the object. The main purpose of the present article is to answer the question, which many interpreters of Beauvoir's text have posed themselves: does Beauvoir really blame only patriarchy for such an injustice or is she rather willing to admit that female biology also contributes to such a biased situation. Researchers have never been unanimous on this issue. However, deeper analysis of The Second Sex as presented in this article finds that Beauvoir does not explain the social situation of women as a result of their biology at any point. According to Beauvoir, the discrimination of women in society is totally undeserved. This article also illustrates the originality of Beauvoir's thoughts in relations to Jean-Paul Sartre's philosophy. In her times, Beauvoir was mainly known as a novelist and the publication of The Second Sex was, misleadingly, not regarded by critics as a philosophical work. In The Second Sex, Beauvoir presents her own theory of interpersonal relationship, different from the one created in Sartre's Being and Nothingness.